1. Field of the Invention
This invention relates to computer models for analyzing the hydraulics and reliability of water distribution systems.
2. Background Information
Water distribution systems are expected to provide water virtually all of the time in spite of failures in individual components in the system. Thus, efforts have been made to quantify and increase the reliability of such systems. There are several ways of increasing reliability including looping pipes, including thicker walled pipes, providing standby power for pumps, improving operator training, installing additional system storage, segmenting the system and providing adequate valves to isolate small areas of the system. Failing to make one or more of these improvements may determine whether a minor outage turns into a major system failure.
Another priority goal in any water distribution system in a community is to provide adequate fire flow. A further challenge is to provide water distribution to growing neighborhoods, which may not have been part of an early plan and may not have adequate distribution pipes. In order to design, repair and evaluate water distribution systems in view of the above-described dynamic aspects of those systems, water engineers use hydraulic models, which are computer models that describe the network elements and simulate the operation of the water distribution network, and can be used to assess the reliability of such distribution systems.
Portions of a water distribution system need to be taken out of service from time to time for maintenance and repairs. The portion of the system that is taken out of service is limited by the placement of isolating valves. More specifically, isolating valves allow a segment of a water distribution system to be sectioned off, while still providing water supply to customers through the remainder of the network. The higher the density of isolating valves, the fewer customers who are put out of service and the smaller the impact on the overall system operation. A tradeoff exists between the number of valves in a system, and the cost. It is noted, however, typically when a pipe line fails, a “segment” of the distribution system is affected, as is defined by the portion of the system that can be isolated using isolation valves.
Many water distribution network computer modeling programs present the system as a set of links (pipes) and nodes (junctions of pipes). In order to simulate a pipe outage, the modeler will remove a link from the model. However, an outage actually removes an entire distribution segment, which is defined by the valves that can be used to isolate the outage, not simply one pipe link. Conventional software models require segmentation outages to be performed manually. In such systems, the location of isolating valves within the system is not always readily apparent to the user.
Such prior modeling programs contain elements like pipes, junctions, pumps and the like. But these elements are not appropriate for performing a criticality analysis because a shut down of some portion of the water system does not affect a single one of those elements or even a set of them, but rather a collection of elements and importantly, parts of such elements. The various approaches that exist to identify critical outage segments of a water distribution system do not take into account the location of isolation valves. This failure to precisely to account for isolation valve locations generates misleading results. In addition, isolating valves are typically not treated as junction nodes in models, and thus they are difficult to locate within the model.
Moreover, segmentation of the network has presented a problem for hydraulic models because, as noted, segments do not correspond directly to pipe links. In fact, a segment almost rarely consists of an entire single pipe link, but rather some collection of pieces of pipe links. Therefore, working with segments requires a different network topology in the model than pipe network analysis alone.
Therefore, there remains a need for a hydraulic model software program that can be readily implemented within a computer hydraulic model platform which program stores isolating valve elements at their correct locations along pipes in the model. There remains a further need for method for automatic generation of segments and a system for correctly identifying the impact of loss of such a segment, thereby identifying the criticality of such a segment.